In its principle embodiment, the present invention discloses compounds having formula I: 
or a pharmaceutically acceptable salt, ester, amide, or prodrug thereof wherein,
n is 0-2;
R1 is selected from the group consisting of alkyl and haloalkyl;
R2 is selected from the group consisting of optionally substituted aryl and optionally substituted heteroaryl;
A is selected from the group consisting of hydrogen, alkyl, haloalkyl, cyano, heteroaryl, nitro and xe2x80x94XR3;
X is selected from the group consisting of C(O) and S(O)p;
p is 1-2;
R3 is selected from the group consisting of alkyl, haloalkyl, and hydroxy;
R4 is selected from the group consisting of hydrogen, alkoxyalkoxyalkyl, alkoxyalkyl, alkyl, arylalkoxyalkyl, aryloxyalkyl, haloalkyl, heteroarylalkoxyalkyl, heteroaryloxyalkyl, (NZ1Z2)alkoxyalkyl, and (NZ1Z2)alkyl wherein Z1 and Z2 are independently selected from the group consisting of hydrogen, alkoxycarbonyl, alkyl, alkylcarbonyl, alkylsulfonyl, aminocarbonyl, aryl, arylalkyl, cycloalkyl, cycloalkylalkyl, formyl, heteroaryl, and heteroarylalkyl or Z1, Z2 and the nitrogen atom to which they are attached form a 3, 4, 5, 6, 7, or 8 membered ring; or
R3 and R4 together form a ring selected from the group consisting of a 5-, 6-, or 7-membered carbocyclic ring with 1-2 double bonds and 0-4 substituents selected from the group consisting of alkenyl, alkoxy, alkoxyalkoxy, alkoxyalkyl, alkyl, alkynyl, arylalkoxy, amino, aminoalkoxy, aminoalkyl, haloalkenyl, haloalkyl, halogen, hydroxy, hydroxyalkenyl, hydroxyalkyl, and oxo, and a 5-, 6- or 7-membered sulfur-containing ring with 1-2 double bonds and 0-4 substituents selected from the group consisting of alkenyl, alkoxy, alkoxyalkoxy, alkoxyalkyl, alkyl, alkynyl, arylalkoxy, amino, aminoalkoxy, aminoalkyl, haloalkenyl, haloalkyl, halogen, hydroxy, hydroxyalkenyl, hydroxyalkyl, and oxo; and
R5 is selected from the group consisting of hydrogen, alkyl and haloalkyl; or R1 and R5 together with the ring to which they are attached form a 5-, 6- or 7-membered sulfur-containing ring with 1-2 double bonds and 0-4 substituents selected from the group consisting of alkenyl, alkoxy, alkoxyalkoxy, alkoxyalkyl, alkyl, alkynyl, arylalkoxy, amino, aminoalkoxy, aminoalkyl, haloalkenyl, haloalkyl, halogen, hydroxy, hydroxyalkenyl, hydroxyalkyl, and oxo;
provided that at least one of R1 and R5 or R3 and R4 forms a ring.
Another embodiment of the present invention relates to pharmaceutical compositions comprising a therapeutically effective amount of a compound of formula I or a pharmaceutically acceptable salt, ester, amide, or prodrug thereof in combination with a pharmaceutically acceptable carrier.
Another embodiment of the invention relates to a method of treating male sexual dysfinction including, but not limited, to male erectile dysfunction and premature ejaculation.
Another embodiment of the invention relates to a method of treating female sexual dysfunction including, but not limited to, female anorgasmia, clitoral erectile insufficiency, vaginal engorgement, dyspareunia, and vaginismus.
Yet another embodiment of the invention relates to a method of treating asthma, epilepsy, hypertension, Raynaud""s syndrome, migraine, pain, eating disorders, urinary incontinence, functional bowel disorders, neurodegeneration and stroke comprising administering a therapeutically effective amount of a compound of formula I or a pharmaceutically acceptable salt, ester, amide, or prodrug thereof.